Well, I figured out how to get rid of the popping sound when shutting down the 970. I also had a slight popping sound on start up too but it wasn't as violent.
Anyhow, if I turn on my 970 and then my 7100, and turn off my 7100 and then my 970, everything is ok. I used to just leave my 7100 on all the time. Probably not the proper solution but it works in my case. Maybe someone with more experience can explain what is going on.
_________________________
Onkyo PR-SC886 (Retired Outlaw 970)
Outlaw 7100
Outlaw 200 Monoblock x2
M&K 851 for L/C/R
Axiom QS8 for SL/SR/1SB
SVS Pb12-ISD/2 (x2)
Sony VPL-HW15 (Retired Infocus 7205)
Sony PS3 / Pioneer DV-533